Diet soda — which has nearly no nutritional value — dangerously bloats waistlines and might boost blood-sugar levels, according to new studies.

People who drink diet soda experienced a 70 percent greater increase in waist circumference over a decade than non-users, a study by the University of Texas Health Science Center San Antonio found.

“The more diet sodas people drank, the more their waists grew,” researcher Sharon Fowler told The Post.

“For people who drink two or more diet sodas a day, their waist increase was five times those who drank no diet sodas — almost two inches.”

Some scientists speculate artificial sweeteners trigger appetite, or inhibit brain cells that signal the feeling of being full.

Helen Hazuda, another of the study’s authors, said “the promotion of diet sodas and artificial sweeteners may be ill-advised.

“They may be free of calories, but not of consequences.”

As if that wasn’t bad enough, University of Texas researchers found in another study that aspartame, a popular artificial sweetener, boosted blood-sugar levels in mice.

The researchers found that mice fed chow containing aspartame and corn oil for three months had higher blood-sugar levels and lower insulin levels — an imbalance that in humans can lead to diabetes, said one of the study’s authors, Gabriel Fernandes.

Both studies were presented at a recent American Diabetes Association conference in San Diego.

Plenty of studies have concluded that diet soda and artificial sweetener make you fat or sick.

A frightening report last winter by University of Miami researchers linked diet soda to an increased risk of stroke and heart attack. Their study was based on a database of Washington Heights residents gathered by Columbia University researchers.

Despite such studies, many scientists are skeptical of the idea that diet soda and artificial sweetener are bad for you.

“I’ve seen people use Sweet’N Low in coffee, and then have a scone. Or someone would have a Diet Coke with their potato chips,” said Lisa Young, a nutritionist who teaches at NYU.

“Maybe people who use artificial sweeteners might be more prone to having other bad habits,” she said.